Analysis of the influence of brake pad material on the formation of defects on the rolling surface of railway wheels

Abstract

The results of research and production experience in the field of identifying the causes and mechanisms of defects on the rolling surface of wheels of railway rolling stock are analysed. The article presents different views on the mechanism of influence of brake pad material on the occurrence of wheel surface defects caused by their frictional interaction with pads made of cast iron or composite material in the form of a composite rubber compound. It has been clearly shown that brake pads made of composite rubber compound damage the rolling surface of wheels to a greater extent and more often. This leads to the need to grind wheel sets and reduces their service life. The main cause of defects on the working surface of the wheels is the thermal load on the friction zone between the pad and the wheel during train braking. The temperature in this zone changes periodically and can reach 900 °C, while the self-ignition temperature of the rubber compound used to make the friction element of composite pads is 350-500 °C. The unacceptably high temperature in the friction zone between the composite pad and the wheel surface, which occurs during train braking, is due to the relatively low thermal conductivity of the composite rubber compound compared to the thermal conductivity of cast iron. Equipping the friction element of composite pads with cast iron inserts does not save the situation with regard to the low thermal conductivity of such pads in general and their tendency to damage the rolling surface of the wheels of vehicles. Recommendations have been proposed to improve the technical and economic performance of railway transport by improving the quality of brake pads for vehicles.